;;; calc-forms.el --- data format conversion functions for Calc

;; Copyright (C) 1990-1993, 2001-2020 Free Software Foundation, Inc.

;; Author: David Gillespie <daveg@synaptics.com>

;; This file is part of GNU Emacs.

;; GNU Emacs is free software: you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation, either version 3 of the License, or
;; (at your option) any later version.

;; GNU Emacs is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;; GNU General Public License for more details.

;; You should have received a copy of the GNU General Public License
;; along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.

;;; Commentary:

;;; Code:

;; This file is autoloaded from calc-ext.el.

(require 'calc-ext)
(require 'calc-macs)

;; Declare functions which are defined elsewhere.
(declare-function calendar-current-time-zone "cal-dst" ())
(declare-function calendar-absolute-from-gregorian "calendar" (date))
(declare-function dst-in-effect "cal-dst" (date))


(defun calc-time ()
  (interactive)
  (calc-wrapper
   (let ((time (decode-time nil nil 'integer))) ;; FIXME: Support subseconds.
     (calc-enter-result 0 "time"
			(list 'mod
			      (list 'hms
				    (decoded-time-hour time)
                                    (decoded-time-minute time)
                                    (decoded-time-second time))
			      (list 'hms 24 0 0))))))

(defun calc-to-hms (arg)
  (interactive "P")
  (calc-wrapper
   (if (calc-is-inverse)
       (if (eq calc-angle-mode 'rad)
	   (calc-unary-op ">rad" 'calcFunc-rad arg)
	 (calc-unary-op ">deg" 'calcFunc-deg arg))
     (calc-unary-op ">hms" 'calcFunc-hms arg))))

(defun calc-from-hms (arg)
  (interactive "P")
  (calc-invert-func)
  (calc-to-hms arg))


(defun calc-hms-notation (fmt)
  (interactive "sHours-minutes-seconds format (hms, @ ' \", etc.): ")
  (calc-wrapper
   (if (string-match "\\`\\([^,; ]+\\)\\([,; ]*\\)\\([^,; ]\\)\\([,; ]*\\)\\([^,; ]\\)\\'" fmt)
       (progn
	 (calc-change-mode 'calc-hms-format
			   (concat "%s" (math-match-substring fmt 1)
				   (math-match-substring fmt 2)
				   "%s" (math-match-substring fmt 3)
				   (math-match-substring fmt 4)
				   "%s" (math-match-substring fmt 5))
			   t)
	 (setq-default calc-hms-format calc-hms-format))  ; for minibuffer
     (error "Bad hours-minutes-seconds format"))))

(defun calc-date-notation (fmt arg)
  (interactive "sDate format (e.g., M/D/YY h:mm:ss): \nP")
  (calc-wrapper
   (if (string-match-p "\\`\\s-*\\'" fmt)
       (setq fmt "1"))
   (if (string-match "\\` *\\([0-9]\\|10\\|11\\) *\\'" fmt)
       (setq fmt (nth (string-to-number fmt) calc-standard-date-formats)))
   (or (string-match "[a-zA-Z]" fmt)
       (error "Bad date format specifier"))
   (and arg
	(>= (setq arg (prefix-numeric-value arg)) 0)
	(<= arg 11)
	(setq calc-standard-date-formats
	      (copy-sequence calc-standard-date-formats))
	(setcar (nthcdr arg calc-standard-date-formats) fmt))
   (let ((case-fold-search nil))
     (and (not (string-match "<.*>" fmt))
          ;; Find time part to put in <...>
	  (string-match "\\`[^hHspPT]*\\([^ac-gi-lnoqrt-zAC-GI-OQRU-Z]*\\(bs\\|bm\\|bh\\|BS\\|BH\\|[hHmpPsST]\\)+[^ac-gi-lnoqrt-zAC-GI-OQRU-Z]*\\)[^hHspPT]*\\'" fmt)
	  (string-match (concat "[^ac-gi-lnoqrt-zAC-GI-OQRT-Z]*"
				(regexp-quote (math-match-substring fmt 1))
				"[^ac-gi-lnoqrt-zAC-GI-OQRT-Z]*") fmt)
	  (setq fmt (concat (substring fmt 0 (match-beginning 0))
			    "<"
			    (substring fmt (match-beginning 0) (match-end 0))
			    ">"
			    (substring fmt (match-end 0))))))
   (let ((lfmt nil)
	 (fullfmt nil)
	 (time nil)
	 pos pos2 sym temp)
     (let ((case-fold-search nil))
       (and (setq temp (string-match ":[BS]S" fmt))
	    (aset fmt temp ?C)))
     (while (setq pos (string-match "[<>a-zA-Z]" fmt))
       (if (> pos 0)
	   (setq lfmt (cons (substring fmt 0 pos) lfmt)))
       (setq pos2 (1+ pos))
       (cond ((= (aref fmt pos) ?\<)
	      (and time (error "Nested <'s not allowed"))
	      (and lfmt (setq fullfmt (nconc lfmt fullfmt)
			      lfmt nil))
	      (setq time t))
	     ((= (aref fmt pos) ?\>)
	      (or time (error "Misplaced > in format"))
	      (and lfmt (setq fullfmt (cons (nreverse lfmt) fullfmt)
			      lfmt nil))
	      (setq time nil))
	     (t
	      (if (string-match "\\`[^a-zA-Z]*[bBZI][a-zA-Z]" fmt)
		  (setq pos2 (1+ pos2)))
	      (while (and (< pos2 (length fmt))
			  (= (upcase (aref fmt pos2))
			     (upcase (aref fmt (1- pos2)))))
		(setq pos2 (1+ pos2)))
	      (setq sym (intern (substring fmt pos pos2)))
	      (or (memq sym '(Y YY BY YYY YYYY
                                ZYYY IYYY Iww w
				aa AA aaa AAA aaaa AAAA
				bb BB bbb BBB bbbb BBBB
				M MM BM mmm Mmm Mmmm MMM MMMM
				D DD BD d ddd bdd
				W www Www Wwww WWW WWWW
				h hh bh H HH BH
				p P pp PP pppp PPPP
				m mm bm s ss bs SS BS C
				N n J j U b T))
		  (and (eq sym 'X) (not lfmt) (not fullfmt))
		  (error "Bad format code: %s" sym))
	      (and (memq sym '(bb BB bbb BBB bbbb BBBB))
		   (setq lfmt (cons 'b lfmt)))
	      (setq lfmt (cons sym lfmt))))
       (setq fmt (substring fmt pos2)))
     (or (equal fmt "")
	 (setq lfmt (cons fmt lfmt)))
     (and lfmt (if time
		   (setq fullfmt (cons (nreverse lfmt) fullfmt))
		 (setq fullfmt (nconc lfmt fullfmt))))
     (calc-change-mode 'calc-date-format (nreverse fullfmt) t))))


(defun calc-hms-mode ()
  (interactive)
  (calc-wrapper
   (calc-change-mode 'calc-angle-mode 'hms)
   (message "Angles measured in degrees-minutes-seconds")))


(defun calc-now (arg)
  (interactive "P")
  (calc-date-zero-args "now" 'calcFunc-now arg))

(defun calc-date-part (arg)
  (interactive "NPart code (1-9 = Y,M,D,H,M,S,Wd,Yd,Hms): ")
  (if (or (< arg 1) (> arg 9))
      (error "Part code out of range"))
  (calc-wrapper
   (calc-enter-result 1
		      (nth arg '(nil "year" "mnth" "day" "hour" "minu"
				      "sec" "wday" "yday" "hmst"))
		      (list (nth arg '(nil calcFunc-year calcFunc-month
					   calcFunc-day calcFunc-hour
					   calcFunc-minute calcFunc-second
					   calcFunc-weekday calcFunc-yearday
					   calcFunc-time))
			    (calc-top-n 1)))))

(defun calc-date (arg)
  (interactive "p")
  (if (or (< arg 1) (> arg 6))
      (error "Between one and six arguments are allowed"))
  (calc-wrapper
   (calc-enter-result arg "date" (cons 'calcFunc-date (calc-top-list-n arg)))))

(defun calc-julian (arg)
  (interactive "P")
  (calc-date-one-arg "juln" 'calcFunc-julian arg))

(defun calc-unix-time (arg)
  (interactive "P")
  (calc-date-one-arg "unix" 'calcFunc-unixtime arg))

(defun calc-time-zone (arg)
  (interactive "P")
  (calc-date-zero-args "zone" 'calcFunc-tzone arg))

(defun calc-convert-time-zones (old &optional new)
  (interactive "sFrom time zone: ")
  (calc-wrapper
   (if (equal old "$")
       (calc-enter-result 3 "tzcv" (cons 'calcFunc-tzconv (calc-top-list-n 3)))
     (if (equal old "") (setq old "local"))
     (or new
	 (setq new (read-string (concat "From time zone: " old
					", to zone: "))))
     (if (stringp old) (setq old (math-read-expr old)))
     (if (eq (car-safe old) 'error)
	 (error "Error in expression: %S" (nth 1 old)))
     (if (equal new "") (setq new "local"))
     (if (stringp new) (setq new (math-read-expr new)))
     (if (eq (car-safe new) 'error)
	 (error "Error in expression: %S" (nth 1 new)))
     (calc-enter-result 1 "tzcv" (list 'calcFunc-tzconv
				       (calc-top-n 1) old new)))))

(defun calc-new-week (arg)
  (interactive "P")
  (calc-date-one-arg "nwwk" 'calcFunc-newweek arg))

(defun calc-new-month (arg)
  (interactive "P")
  (calc-date-one-arg "nwmn" 'calcFunc-newmonth arg))

(defun calc-new-year (arg)
  (interactive "P")
  (calc-date-one-arg "nwyr" 'calcFunc-newyear arg))

(defun calc-inc-month (arg)
  (interactive "p")
  (calc-date-one-arg "incm" 'calcFunc-incmonth arg))

(defun calc-business-days-plus (arg)
  (interactive "P")
  (calc-wrapper
   (calc-binary-op "bus+" 'calcFunc-badd arg)))

(defun calc-business-days-minus (arg)
  (interactive "P")
  (calc-wrapper
   (calc-binary-op "bus-" 'calcFunc-bsub arg)))

(defun calc-date-zero-args (prefix func arg)
  (calc-wrapper
   (if (consp arg)
       (calc-enter-result 1 prefix (list func (calc-top-n 1)))
     (calc-enter-result 0 prefix (if arg
				     (list func (prefix-numeric-value arg))
				   (list func))))))

(defun calc-date-one-arg (prefix func arg)
  (calc-wrapper
   (if (consp arg)
       (calc-enter-result 2 prefix (cons func (calc-top-list-n 2)))
     (calc-enter-result 1 prefix (if arg
				     (list func (calc-top-n 1)
					   (prefix-numeric-value arg))
				   (list func (calc-top-n 1)))))))


;;;; Hours-minutes-seconds forms.

(defun math-normalize-hms (a)
  (let ((h (math-normalize (nth 1 a)))
	(m (math-normalize (nth 2 a)))
	(s (let ((calc-internal-prec (max (- calc-internal-prec 4) 3)))
	     (math-normalize (nth 3 a)))))
    (if (or
         (math-negp h)
         (and (= h 0) (math-negp m))
         (and (= h 0) (= m 0) (math-negp s)))
	(progn
	  (if (math-posp s)
	      (setq s (math-add s -60)
		    m (math-add m 1)))
	  (if (math-posp m)
	      (setq m (math-add m -60)
		    h (math-add h 1)))
	  (if (not (Math-lessp -60 s))
	      (setq s (math-add s 60)
		    m (math-add m -1)))
	  (if (not (Math-lessp -60 m))
	      (setq m (math-add m 60)
		    h (math-add h -1))))
      (if (math-negp s)
	  (setq s (math-add s 60)
		m (math-add m -1)))
      (if (math-negp m)
	  (setq m (math-add m 60)
		h (math-add h -1)))
      (if (not (Math-lessp s 60))
	  (setq s (math-add s -60)
		m (math-add m 1)))
      (if (not (Math-lessp m 60))
	  (setq m (math-add m -60)
		h (math-add h 1))))
    (if (and (eq (car-safe s) 'float)
	     (<= (+ (math-numdigs (nth 1 s)) (nth 2 s))
		 (- 2 calc-internal-prec)))
	(setq s 0))
    (list 'hms h m s)))

;;; Convert A from ANG or current angular mode to HMS format.
(defun math-to-hms (a &optional ang)   ; [X R] [Public]
  (cond ((eq (car-safe a) 'hms) a)
	((eq (car-safe a) 'sdev)
	 (math-make-sdev (math-to-hms (nth 1 a))
			 (math-to-hms (nth 2 a))))
	((not (Math-numberp a))
	 (list 'calcFunc-hms a))
	((math-negp a)
	 (math-neg (math-to-hms (math-neg a) ang)))
	((eq (or ang
                 (and (not math-simplifying-units) calc-angle-mode))
                 'rad)
	 (math-to-hms (math-div a (math-pi-over-180)) 'deg))
	((memq (car-safe a) '(cplx polar)) a)
	(t
	 ;(setq a (let ((calc-internal-prec (max (1- calc-internal-prec) 3)))
	 ;	    (math-normalize a)))
	 (math-normalize
	  (let* ((b (math-mul a 3600))
		 (hm (math-trunc (math-div b 60)))
		 (hmd (math-idivmod hm 60)))
	    (list 'hms
		  (car hmd)
		  (cdr hmd)
		  (math-sub b (math-mul hm 60))))))))
(defun calcFunc-hms (h &optional m s)
  (or (Math-realp h) (math-reject-arg h 'realp))
  (or m (setq m 0))
  (or (Math-realp m) (math-reject-arg m 'realp))
  (or s (setq s 0))
  (or (Math-realp s) (math-reject-arg s 'realp))
  (if (and (not (Math-lessp m 0)) (Math-lessp m 60)
	   (not (Math-lessp s 0)) (Math-lessp s 60))
      (math-add (math-to-hms h)
		(list 'hms 0 m s))
    (math-to-hms (math-add h
			   (math-add (math-div (or m 0) 60)
				     (math-div (or s 0) 3600)))
		 'deg)))

;;; Convert A from HMS format to ANG or current angular mode.
(defun math-from-hms (a &optional ang)   ; [R X] [Public]
  (cond ((not (eq (car-safe a) 'hms))
	 (if (Math-numberp a)
	     a
	   (if (eq (car-safe a) 'sdev)
	       (math-make-sdev (math-from-hms (nth 1 a) ang)
			       (math-from-hms (nth 2 a) ang))
	     (if (eq (or ang
                         (and (not math-simplifying-units) calc-angle-mode))
                     'rad)
		 (list 'calcFunc-rad a)
	       (list 'calcFunc-deg a)))))
	((math-negp a)
	 (math-neg (math-from-hms (math-neg a) ang)))
	((eq (or ang
                 (and (not math-simplifying-units) calc-angle-mode))
             'rad)
	 (math-mul (math-from-hms a 'deg) (math-pi-over-180)))
	(t
	 (math-add (math-div (math-add (math-div (nth 3 a)
						 '(float 6 1))
				       (nth 2 a))
			     60)
		   (nth 1 a)))))

;;;; Date forms.


;;; Some of these functions are adapted from Edward Reingold's "calendar.el".
;;; These versions are rewritten to use arbitrary-size integers.

;;; A numerical date is the number of days since midnight on
;;; the morning of December 31, 1 BC (Gregorian) or January 2, 1 AD (Julian).
;;; Emacs's calendar refers to such a date as an absolute date, some Calc function
;;; names also use that terminology.  If the date is a non-integer, it represents
;;; a specific date and time.
;;; A "dt" is a list of the form, (year month day), corresponding to
;;; an integer code, or (year month day hour minute second), corresponding
;;; to a non-integer code.

(defun math-date-to-gregorian-dt (date)
  "Return the day (YEAR MONTH DAY) in the Gregorian calendar.
DATE is the number of days since December 31, -1 in the Gregorian calendar."
  (let* ((month 1)
         day
         (year (math-quotient (math-add date (if (Math-lessp date 711859)
                                                 365  ; for speed, we take
                                               -108)) ; >1950 as a special case
                              (if (math-negp date) 366 365)))
					; this result may be an overestimate
         temp)
    (while (Math-lessp date (setq temp (math-absolute-from-gregorian-dt year 1 1)))
        (setq year (math-add year -1)))
    (if (eq year 0) (setq year -1))
    (setq date (1+ (math-sub date temp)))
    (setq temp
          (if (math-leap-year-p year)
              [1 32 61 92 122 153 183 214 245 275 306 336 999]
            [1 32 60 91 121 152 182 213 244 274 305 335 999]))
    (while (>= date (aref temp month))
      (setq month (1+ month)))
    (setq day (1+ (- date (aref temp (1- month)))))
    (list year month day)))

(defun math-date-to-julian-dt (date)
  "Return the day (YEAR MONTH DAY) in the Julian calendar.
DATE is the number of days since December 31, -1 in the Gregorian calendar."
  (let* ((month 1)
         day
         (year (math-quotient (math-add date (if (Math-lessp date 711859)
                                                 367  ; for speed, we take
                                               -106)) ; >1950 as a special case
                              (if (math-negp date) 366 365)))
					; this result may be an overestimate
         temp)
    (while (Math-lessp date (setq temp (math-absolute-from-julian-dt year 1 1)))
        (setq year (math-add year -1)))
    (if (eq year 0) (setq year -1))
    (setq date (1+ (math-sub date temp)))
    (setq temp
          (if (math-leap-year-p year t)
              [1 32 61 92 122 153 183 214 245 275 306 336 999]
            [1 32 60 91 121 152 182 213 244 274 305 335 999]))
    (while (>= date (aref temp month))
      (setq month (1+ month)))
    (setq day (1+ (- date (aref temp (1- month)))))
    (list year month day)))

(defun math-date-to-dt (value)
  "Return the day and time of VALUE.
The integer part of VALUE is the number of days since Dec 31, -1
in the Gregorian calendar and the remaining part determines the time."
  (if (eq (car-safe value) 'date)
      (setq value (nth 1 value)))
  (or (math-realp value)
      (math-reject-arg value 'datep))
  (let* ((parts (math-date-parts value))
	 (date (car parts))
	 (time (nth 1 parts))
         (dt (if (and calc-gregorian-switch
                      (Math-lessp value
                                  (or
                                   (nth 3 calc-gregorian-switch)
                                   (apply 'math-absolute-from-gregorian-dt calc-gregorian-switch))
))
                 (math-date-to-julian-dt date)
               (math-date-to-gregorian-dt date))))
    (if (math-integerp value)
        dt
      (append dt
              (list
               (/ time 3600)
               (% (/ time 60) 60)
               (math-add (% time 60) (nth 2 parts)))))))

(defun math-date-to-iso-dt (date)
  "Return the ISO8601 date (year week day) of DATE."
  (unless (Math-integerp date)
    (setq date (math-floor date)))
  (let* ((approx (nth 0 (math-date-to-gregorian-dt (math-sub date 3))))
         (year (math-add approx
                         (let ((y approx)
                               (sum 0))
                           (while (>= (math-compare date
                                                    (math-absolute-from-iso-dt (setq y (math-add y 1)) 1 1)) 0)
                             (setq sum (+ sum 1)))
                           sum))))
    (list
     year
     (math-add (car (math-idivmod
                     (math-sub date (math-absolute-from-iso-dt year 1 1))
                     7))
               1)
     (let ((day (calcFunc-mod date 7)))
       (if (= day 0) 7 day)))))

(defun math-dt-to-date (dt)
  (or (integerp (nth 1 dt))
      (math-reject-arg (nth 1 dt) 'fixnump))
  (if (or (< (nth 1 dt) 1) (> (nth 1 dt) 12))
      (math-reject-arg (nth 1 dt) "Month value is out of range"))
  (or (integerp (nth 2 dt))
      (math-reject-arg (nth 2 dt) 'fixnump))
  (if (or (< (nth 2 dt) 1) (> (nth 2 dt) 31))
      (math-reject-arg (nth 2 dt) "Day value is out of range"))
  (let ((date (math-absolute-from-dt (car dt) (nth 1 dt) (nth 2 dt))))
    (if (nth 3 dt)
	(math-add (math-float date)
		  (math-div (math-add (+ (* (nth 3 dt) 3600)
					 (* (nth 4 dt) 60))
				      ;; FIXME: Support subseconds.
				      (time-convert (nth 5 dt) 'integer))
			    '(float 864 2)))
      date)))

(defun math-iso-dt-to-date (dt)
  (let ((date (math-absolute-from-iso-dt (car dt) (nth 1 dt) (nth 2 dt))))
    (if (nth 3 dt)
	(math-add (math-float date)
		  (math-div (math-add (+ (* (nth 3 dt) 3600)
					 (* (nth 4 dt) 60))
				      (nth 5 dt))
			    '(float 864 2)))
      date)))

(defun math-date-parts (value &optional offset)
  (let* ((date (math-floor value))
	 (time (math-round (math-mul (math-sub value (or offset date)) 86400)
			   (and (> calc-internal-prec 12)
				(- calc-internal-prec 12))))
	 (ftime (math-floor time)))
    (list date
	  ftime
	  (math-sub time ftime))))


(defun math-this-year ()
  (decoded-time-year (decode-time)))

(defun math-leap-year-p (year &optional julian)
  "Non-nil if YEAR is a leap year.
If JULIAN is non-nil, then use the criterion for leap years
in the Julian calendar, otherwise use the criterion in the
Gregorian calendar."
  (if julian
      (if (math-negp year)
	  (= (math-imod (math-neg year) 4) 1)
	(= (math-imod year 4) 0))
    (if (math-negp year)
        (setq year (math-sub -1 year)))
    (setq year (math-imod year 400))
    (or (and (= (% year 4) 0) (/= (% year 100) 0))
	(= year 0))))

(defun math-days-in-month (year month)
  (if (and (= month 2) (math-leap-year-p year))
      29
    (aref [31 28 31 30 31 30 31 31 30 31 30 31] (1- month))))

(defun math-day-in-year (year month day &optional julian)
  "Return the number of days of the year up to YEAR MONTH DAY.
The count includes the given date.
If JULIAN is non-nil, use the Julian calendar, otherwise
use the Gregorian calendar."
  (let ((day-of-year (+ day (* 31 (1- month)))))
    (if (> month 2)
	(progn
	  (setq day-of-year (- day-of-year (/ (+ 23 (* 4 month)) 10)))
	  (if (math-leap-year-p year julian)
	      (setq day-of-year (1+ day-of-year)))))
    day-of-year))

(defun math-day-number (year month day)
  "Return the number of days of the year up to YEAR MONTH DAY.
The count includes the given date."
  (if calc-gregorian-switch
      (cond ((eq year (nth 0 calc-gregorian-switch))
             (1+
              (- (math-absolute-from-dt year month day)
                 (math-absolute-from-dt year 1 1))))
            ((Math-lessp year (nth 0 calc-gregorian-switch))
             (math-day-in-year year month day t))
            (t
             (math-day-in-year year month day)))
    (math-day-in-year year month day)))

(defun math-dt-before-p (dt1 dt2)
  "Non-nil if DT1 occurs before DT2.
A DT is a list of the form (YEAR MONTH DAY)."
  (or (Math-lessp (nth 0 dt1) (nth 0 dt2))
      (and (equal (nth 0 dt1) (nth 0 dt2))
           (or (< (nth 1 dt1) (nth 1 dt2))
               (and (= (nth 1 dt1) (nth 1 dt2))
                    (< (nth 2 dt1) (nth 2 dt2)))))))

(defun math-absolute-from-gregorian-dt (year month day)
  "Return the DATE of the day given by the Gregorian day YEAR MONTH DAY.
Recall that DATE is the number of days since December 31, -1
in the Gregorian calendar."
  (when (zerop year)                    ; Year -1 precedes year 1.
    (setq year -1))
  (let* ((y (if (> year 0) year (+ year 1)))  ; Astronomical year (with 0).
         (y1 (- y 1)))                        ; Previous year.
    (+ (* y1 365)                    ; Days up to the previous year...
       (floor y1 4)                  ; ... including leap days.
       (- (floor y1 100))
       (floor y1 400)
       (math-day-in-year year month day))))

(defun math-absolute-from-julian-dt (year month day)
  "Return the DATE of the day given by the Julian day YEAR MONTH DAY.
Recall that DATE is the number of days since December 31, -1
in the Gregorian calendar."
  (if (eq year 0) (setq year -1))
  (let ((yearm1 (math-sub year 1)))
    (math-sub
     ;; Add the number of days of the year and the numbers of days
     ;; in the previous years (leap year days to be added separately)
     (math-add (math-day-in-year year month day t)
               (math-add (math-mul 365 yearm1)
                         ;; Add the number of Julian leap years
                         (if (math-posp year)
                             (math-quotient yearm1 4)
                           (math-sub 365
                                     (math-quotient (math-sub 3 year)
                                                    4)))))
     ;; Adjustment, since January 1, 1 (Julian) is absolute day -1
     2)))

;; calc-gregorian-switch is a customizable variable defined in calc.el
(defvar calc-gregorian-switch)

(defun math-absolute-from-iso-dt (year week day)
  "Return the DATE of the day given by the iso8601 day YEAR WEEK DAY."
  (let* ((janfour (math-absolute-from-gregorian-dt year 1 4))
         (prevmon (math-sub janfour
                            (cdr (math-idivmod (math-sub janfour 1) 7)))))
    (math-add
     (math-add prevmon (* (1- week) 7))
     (if (zerop day) 6 (1- day)))))

(defun math-absolute-from-dt (year month day)
  "Return the DATE of the day given by the day YEAR MONTH DAY.
Recall that DATE is the number of days since December 31, -1
in the Gregorian calendar."
  (if (and calc-gregorian-switch
           ;; The next few lines determine if the given date
           ;; occurs before the switch to the Gregorian calendar.
           (math-dt-before-p (list year month day) calc-gregorian-switch))
      (math-absolute-from-julian-dt year month day)
    (math-absolute-from-gregorian-dt year month day)))

;;; It is safe to redefine these in your init file to use a different
;;; language.

(defvar math-long-weekday-names '( "Sunday" "Monday" "Tuesday" "Wednesday"
				   "Thursday" "Friday" "Saturday" ))
(defvar math-short-weekday-names '( "Sun" "Mon" "Tue" "Wed"
				    "Thu" "Fri" "Sat" ))

(defvar math-long-month-names '( "January" "February" "March" "April"
				 "May" "June" "July" "August"
				 "September" "October" "November" "December" ))
(defvar math-short-month-names '( "Jan" "Feb" "Mar" "Apr" "May" "Jun"
				  "Jul" "Aug" "Sep" "Oct" "Nov" "Dec" ))


(defvar math-format-date-cache nil)

;; The variables math-fd-date, math-fd-dt, math-fd-year,
;; math-fd-month, math-fd-day, math-fd-weekday, math-fd-hour,
;; math-fd-minute, math-fd-second, math-fd-bc-flag are local
;; to math-format-date, but are used by math-format-date-part,
;; which is called by math-format-date.
(defvar math-fd-date)
(defvar math-fd-dt)
(defvar math-fd-year)
(defvar math-fd-month)
(defvar math-fd-day)
(defvar math-fd-weekday)
(defvar math-fd-hour)
(defvar math-fd-minute)
(defvar math-fd-second)
(defvar math-fd-bc-flag)
(defvar math-fd-iso-dt)
(defvar math-fd-isoyear)
(defvar math-fd-isoweek)
(defvar math-fd-isoweekday)

(defun math-format-date (math-fd-date)
  (if (eq (car-safe math-fd-date) 'date)
      (setq math-fd-date (nth 1 math-fd-date)))
  (let ((entry (list math-fd-date calc-internal-prec calc-date-format)))
    (or (cdr (assoc entry math-format-date-cache))
	(let* ((math-fd-dt nil)
               (math-fd-iso-dt nil)
	       (calc-group-digits nil)
	       (calc-leading-zeros nil)
	       (calc-number-radix 10)
               (calc-twos-complement-mode nil)
	       math-fd-year math-fd-month math-fd-day math-fd-weekday
               math-fd-hour math-fd-minute math-fd-second
               math-fd-isoyear math-fd-isoweek math-fd-isoweekday
	       (math-fd-bc-flag nil)
	       (fmt (apply 'concat (mapcar 'math-format-date-part
					   calc-date-format))))
	  (setq math-format-date-cache (cons (cons entry fmt)
					     math-format-date-cache))
	  (and (setq math-fd-dt (nthcdr 10 math-format-date-cache))
	       (setcdr math-fd-dt nil))
	  fmt))))

(defconst math-julian-date-beginning '(float 17214245 -1)
  "The beginning of the Julian date calendar,
as measured in the number of days before December 31, 1 BC (Gregorian).")

(defconst math-julian-date-beginning-int 1721425
  "The beginning of the Julian date calendar,
as measured in the integer number of days before December 31, 1 BC (Gregorian).")

(defun math-format-date-part (x)
  (cond ((stringp x)
	 x)
	((listp x)
	 (if (math-integerp math-fd-date)
	     ""
	   (apply 'concat (mapcar 'math-format-date-part x))))
	((eq x 'X)
	 "")
	((eq x 'N)
	 (math-format-number math-fd-date))
	((eq x 'n)
	 (math-format-number (math-floor math-fd-date)))
	((eq x 'J)
	 (math-format-number
          (math-add math-fd-date math-julian-date-beginning)))
	((eq x 'j)
	 (math-format-number (math-add
                              (math-floor math-fd-date)
                              math-julian-date-beginning-int)))
	((eq x 'U)
	 (math-format-number (nth 1 (math-date-parts math-fd-date 719164))))
        ((memq x '(IYYY Iww w))
         (progn
           (or math-fd-iso-dt
               (setq math-fd-iso-dt (math-date-to-iso-dt math-fd-date)
                     math-fd-isoyear (car math-fd-iso-dt)
                     math-fd-isoweek (nth 1 math-fd-iso-dt)
                     math-fd-isoweekday (nth 2 math-fd-iso-dt)))
           (cond ((eq x 'IYYY)
                  (let* ((neg (Math-negp math-fd-isoyear))
                         (pyear (calcFunc-abs math-fd-isoyear)))
                    (if (and (natnump pyear) (< pyear 10000))
                        (concat (if neg "-" "") (format "%04d" pyear))
                      (concat (if neg "-" "+") (math-format-number pyear)))))
                 ((eq x 'Iww)
                  (concat "W" (format "%02d" math-fd-isoweek)))
                 ((eq x 'w)
                  (format "%d" math-fd-isoweekday)))))
	((progn
	   (or math-fd-dt
	       (progn
		 (setq math-fd-dt (math-date-to-dt math-fd-date)
		       math-fd-year (car math-fd-dt)
		       math-fd-month (nth 1 math-fd-dt)
		       math-fd-day (nth 2 math-fd-dt)
		       math-fd-weekday (math-mod (math-floor math-fd-date) 7)
		       math-fd-hour (nth 3 math-fd-dt)
		       math-fd-minute (nth 4 math-fd-dt)
		       math-fd-second (nth 5 math-fd-dt))
		 (and (memq 'b calc-date-format)
		      (math-negp math-fd-year)
		      (setq math-fd-year (math-neg math-fd-year)
			    math-fd-bc-flag t))))
	   (memq x '(Y YY BY)))
	 (if (and (integerp math-fd-year) (> math-fd-year 1940) (< math-fd-year 2040))
	     (format (cond ((eq x 'YY) "%02d")
			   ((eq x 'BYY) "%2d")
			   (t "%d"))
		     (% math-fd-year 100))
	   (if (and (natnump math-fd-year) (< math-fd-year 100))
	       (format "+%d" math-fd-year)
	     (math-format-number math-fd-year))))
	((eq x 'YYY)
	 (math-format-number math-fd-year))
	((eq x 'YYYY)
	 (if (and (natnump math-fd-year) (< math-fd-year 100))
	     (format "+%d" math-fd-year)
	   (math-format-number math-fd-year)))
        ((eq x 'ZYYY)
         (let* ((year (if (Math-negp math-fd-year)
                          (math-add math-fd-year 1)
                        math-fd-year))
                (neg (Math-negp year))
                (pyear (calcFunc-abs year)))
           (if (and (natnump pyear) (< pyear 10000))
               (concat (if neg "-" "") (format "%04d" pyear))
             (concat (if neg "-" "+") (math-format-number pyear)))))
	((eq x 'b) "")
	((eq x 'aa)
	 (and (not math-fd-bc-flag) "ad"))
	((eq x 'AA)
	 (and (not math-fd-bc-flag) "AD"))
	((eq x 'aaa)
	 (and (not math-fd-bc-flag) "ad "))
	((eq x 'AAA)
	 (and (not math-fd-bc-flag) "AD "))
	((eq x 'aaaa)
	 (and (not math-fd-bc-flag) "a.d."))
	((eq x 'AAAA)
	 (and (not math-fd-bc-flag) "A.D."))
	((eq x 'bb)
	 (and math-fd-bc-flag "bc"))
	((eq x 'BB)
	 (and math-fd-bc-flag "BC"))
	((eq x 'bbb)
	 (and math-fd-bc-flag " bc"))
	((eq x 'BBB)
	 (and math-fd-bc-flag " BC"))
	((eq x 'bbbb)
	 (and math-fd-bc-flag "b.c."))
	((eq x 'BBBB)
	 (and math-fd-bc-flag "B.C."))
        ((eq x 'T) "T")
	((eq x 'M)
	 (format "%d" math-fd-month))
	((eq x 'MM)
	 (format "%02d" math-fd-month))
	((eq x 'BM)
	 (format "%2d" math-fd-month))
	((eq x 'mmm)
	 (downcase (nth (1- math-fd-month) math-short-month-names)))
	((eq x 'Mmm)
	 (nth (1- math-fd-month) math-short-month-names))
	((eq x 'MMM)
	 (upcase (nth (1- math-fd-month) math-short-month-names)))
	((eq x 'Mmmm)
	 (nth (1- math-fd-month) math-long-month-names))
	((eq x 'MMMM)
	 (upcase (nth (1- math-fd-month) math-long-month-names)))
	((eq x 'D)
	 (format "%d" math-fd-day))
	((eq x 'DD)
	 (format "%02d" math-fd-day))
	((eq x 'BD)
	 (format "%2d" math-fd-day))
	((eq x 'W)
	 (format "%d" math-fd-weekday))
	((eq x 'www)
	 (downcase (nth math-fd-weekday math-short-weekday-names)))
	((eq x 'Www)
	 (nth math-fd-weekday math-short-weekday-names))
	((eq x 'WWW)
	 (upcase (nth math-fd-weekday math-short-weekday-names)))
	((eq x 'Wwww)
	 (nth math-fd-weekday math-long-weekday-names))
	((eq x 'WWWW)
	 (upcase (nth math-fd-weekday math-long-weekday-names)))
	((eq x 'd)
	 (format "%d" (math-day-number math-fd-year math-fd-month math-fd-day)))
	((eq x 'ddd)
	 (format "%03d" (math-day-number math-fd-year math-fd-month math-fd-day)))
	((eq x 'bdd)
	 (format "%3d" (math-day-number math-fd-year math-fd-month math-fd-day)))
	((eq x 'h)
	 (and math-fd-hour (format "%d" math-fd-hour)))
	((eq x 'hh)
	 (and math-fd-hour (format "%02d" math-fd-hour)))
	((eq x 'bh)
	 (and math-fd-hour (format "%2d" math-fd-hour)))
	((eq x 'H)
	 (and math-fd-hour (format "%d" (1+ (% (+ math-fd-hour 11) 12)))))
	((eq x 'HH)
	 (and math-fd-hour (format "%02d" (1+ (% (+ math-fd-hour 11) 12)))))
	((eq x 'BH)
	 (and math-fd-hour (format "%2d" (1+ (% (+ math-fd-hour 11) 12)))))
	((eq x 'p)
	 (and math-fd-hour (if (< math-fd-hour 12) "a" "p")))
	((eq x 'P)
	 (and math-fd-hour (if (< math-fd-hour 12) "A" "P")))
	((eq x 'pp)
	 (and math-fd-hour (if (< math-fd-hour 12) "am" "pm")))
	((eq x 'PP)
	 (and math-fd-hour (if (< math-fd-hour 12) "AM" "PM")))
	((eq x 'pppp)
	 (and math-fd-hour (if (< math-fd-hour 12) "a.m." "p.m.")))
	((eq x 'PPPP)
	 (and math-fd-hour (if (< math-fd-hour 12) "A.M." "P.M.")))
	((eq x 'm)
	 (and math-fd-minute (format "%d" math-fd-minute)))
	((eq x 'mm)
	 (and math-fd-minute (format "%02d" math-fd-minute)))
	((eq x 'bm)
	 (and math-fd-minute (format "%2d" math-fd-minute)))
	((eq x 'C)
	 (and math-fd-second (not (math-zerop math-fd-second))
	      ":"))
	((memq x '(s ss bs SS BS))
	 (and math-fd-second
	      (not (and (memq x '(SS BS)) (math-zerop math-fd-second)))
	      (if (integerp math-fd-second)
		  (format (cond ((memq x '(ss SS)) "%02d")
				((memq x '(bs BS)) "%2d")
				(t "%d"))
			  math-fd-second)
		(concat (if (Math-lessp math-fd-second 10)
			    (cond ((memq x '(ss SS)) "0")
				  ((memq x '(bs BS)) " ")
				  (t ""))
			  "")
			(let ((calc-float-format
			       (list 'fix (min (- 12 calc-internal-prec)
					       0))))
			  (math-format-number math-fd-second))))))))

;; The variable math-pd-str is local to math-parse-date and
;; math-parse-standard-date, but is used by math-parse-date-word,
;; which is called by math-parse-date and math-parse-standard-date.
(defvar math-pd-str)

(defun math-parse-date (math-pd-str)
  (catch 'syntax
    (or (math-parse-standard-date math-pd-str t)
	(math-parse-standard-date math-pd-str nil)
        (and (string-match "W[0-9][0-9]" math-pd-str)
             (math-parse-iso-date math-pd-str))
	(and (string-match "\\`[^-+/0-9a-zA-Z]*\\([-+]?[0-9]+\\.?[0-9]*\\([eE][-+]?[0-9]+\\)?\\)[^-+/0-9a-zA-Z]*\\'" math-pd-str)
	     (list 'date (math-read-number (math-match-substring math-pd-str 1))))
	(let ((case-fold-search t)
	      (year nil) (month nil) (day nil) (weekday nil)
	      (hour nil) (minute nil) (second nil) (bc-flag nil)
	      (a nil) (b nil) (c nil) (bigyear nil) temp)

	  ;; Extract the time, if any.
	  (if (or (string-match "\\([0-9][0-9]?\\):\\([0-9][0-9]?\\)\\(:\\([0-9][0-9]?\\(\\.[0-9]+\\)?\\)\\)? *\\([ap]\\>\\|[ap]m\\|[ap]\\. *m\\.\\|noon\\|n\\>\\|midnight\\|mid\\>\\|m\\>\\)?" math-pd-str)
		  (string-match "\\([0-9][0-9]?\\)\\(\\)\\(\\(\\(\\)\\)\\) *\\([ap]\\>\\|[ap]m\\|[ap]\\. *m\\.\\|noon\\|n\\>\\|midnight\\|mid\\>\\|m\\>\\)" math-pd-str))
	      (let ((ampm (math-match-substring math-pd-str 6)))
		(setq hour (string-to-number (math-match-substring math-pd-str 1))
		      minute (math-match-substring math-pd-str 2)
		      second (math-match-substring math-pd-str 4)
		      math-pd-str (concat (substring math-pd-str 0 (match-beginning 0))
				  (substring math-pd-str (match-end 0))))
		(if (equal minute "")
		    (setq minute 0)
		  (setq minute (string-to-number minute)))
		(if (equal second "")
		    (setq second 0)
		  (setq second (math-read-number second)))
		(if (equal ampm "")
		    (if (or
                         (> hour 24)
                         (and (= hour 24)
                              (not (= minute 0))
                              (not (eq second 0))))
			(throw 'syntax "Hour value is out of range"))
		  (setq ampm (upcase (aref ampm 0)))
		  (if (memq ampm '(?N ?M))
		      (if (and (= hour 12) (= minute 0) (eq second 0))
			  (if (eq ampm ?M) (setq hour 0))
			(throw 'syntax
			       "Time must be 12:00:00 in this context"))
		    (if (or (= hour 0) (> hour 12))
			(throw 'syntax "Hour value is out of range"))
		    (if (eq (= ampm ?A) (= hour 12))
			(setq hour (% (+ hour 12) 24)))))))

	  ;; Rewrite xx-yy-zz to xx/yy/zz to avoid seeing "-" as a minus sign.
	  (while (string-match "[0-9a-zA-Z]\\(-\\)[0-9a-zA-Z]" math-pd-str)
	    (progn
	      (setq math-pd-str (copy-sequence math-pd-str))
	      (aset math-pd-str (match-beginning 1) ?\/)))

	  ;; Extract obvious month or weekday names.
	  (if (string-match "[a-zA-Z]" math-pd-str)
	      (progn
		(setq month (math-parse-date-word math-long-month-names))
		(setq weekday (math-parse-date-word math-long-weekday-names))
		(or month (setq month
				(math-parse-date-word math-short-month-names)))
		(or weekday (math-parse-date-word math-short-weekday-names))
		(or hour
		    (if (setq temp (math-parse-date-word
				    '( "noon" "midnight" "mid" )))
			(setq hour (if (= temp 1) 12 0) minute 0 second 0)))
		(or (math-parse-date-word '( "ad" "a.d." ))
		    (if (math-parse-date-word '( "bc" "b.c." ))
			(setq bc-flag t)))
		(if (string-match "[a-zA-Z]+" math-pd-str)
		    (throw 'syntax (format "Bad word in date: \"%s\""
					   (math-match-substring math-pd-str 0))))))

	  ;; If there is a huge number other than the year, ignore it.
	  (while (and (string-match "[-+]?0*[1-9][0-9][0-9][0-9][0-9]+" math-pd-str)
		      (setq temp (concat (substring math-pd-str 0 (match-beginning 0))
					 (substring math-pd-str (match-end 0))))
		      (string-match
                       "[4-9][0-9]\\|[0-9][0-9][0-9]\\|[-+][0-9]+[^-]*\\'" temp))
	    (setq math-pd-str temp))

	  ;; If there is a number with a sign or a large number, it is a year.
	  (if (or (string-match "\\([-+][0-9]+\\)[^-]*\\'" math-pd-str)
		  (string-match "\\(0*[1-9][0-9][0-9]+\\)" math-pd-str))
	      (setq year (math-match-substring math-pd-str 1)
		    math-pd-str (concat (substring math-pd-str 0 (match-beginning 1))
				(substring math-pd-str (match-end 1)))
		    year (math-read-number year)
		    bigyear t))

	  ;; Collect remaining numbers.
	  (setq temp 0)
	  (while (string-match "[0-9]+" math-pd-str temp)
	    (and c (throw 'syntax "Too many numbers in date"))
	    (setq c (string-to-number (math-match-substring math-pd-str 0)))
	    (or b (setq b c c nil))
	    (or a (setq a b b nil))
	    (setq temp (match-end 0)))

	  ;; Check that we have the right amount of information.
	  (setq temp (+ (if year 1 0) (if month 1 0) (if day 1 0)
			(if a 1 0) (if b 1 0) (if c 1 0)))
	  (if (> temp 3)
	      (throw 'syntax "Too many numbers in date")
	    (if (or (< temp 2) (and year (= temp 2)))
		(throw 'syntax "Not enough numbers in date")
	      (if (= temp 2)   ; if year omitted, assume current year
		  (setq year (math-this-year)))))

	  ;; A large number must be a year.
	  (or year
	      (if (and a (or (> a 31) (< a 1)))
		  (setq year a a b b c c nil)
		(if (and b (or (> b 31) (< b 1)))
		    (setq year b b c c nil)
		  (if (and c (or (> c 31) (< c 1)))
		      (setq year c c nil)))))

	  ;; A medium-large number must be a day.
	  (if year
	      (if (and a (> a 12))
		  (setq day a a b b c c nil)
		(if (and b (> b 12))
		    (setq day b b c c nil)
		  (if (and c (> c 12))
		      (setq day c c nil)))))

	  ;; We may know enough to sort it out now.
	  (if (and year day)
	      (or month (setq month a))
	    (if (and year month)
		(setq day a)

	      ;; Interpret order of numbers as same as for display format.
	      (setq temp calc-date-format)
	      (while temp
		(cond ((not (symbolp (car temp))))
		      ((memq (car temp) '(Y YY BY YYY YYYY))
		       (or year (setq year a a b b c)))
		      ((memq (car temp) '(M MM BM mmm Mmm Mmmm MMM MMMM))
		       (or month (setq month a a b b c)))
		      ((memq (car temp) '(D DD BD))
		       (or day (setq day a a b b c))))
		(setq temp (cdr temp)))

	      ;; If display format was not complete, assume American style.
	      (or month (setq month a a b b c))
	      (or day (setq day a a b b c))
	      (or year (setq year a a b b c))))

	  (if bc-flag
	      (setq year (math-neg (math-abs year))))

	  (math-parse-date-validate year bigyear month day
				    hour minute second)))))

(defun math-parse-date-validate (year bigyear month day hour minute second)
  (and (not bigyear) (natnump year) (< year 100)
       (setq year (+ year (if (< year 40) 2000 1900))))
  (if (eq year 0)
      (throw 'syntax "Year value is out of range"))
  (if (or (< month 1) (> month 12))
      (throw 'syntax "Month value is out of range"))
  (if (or (< day 1) (> day (math-days-in-month year month)))
      (throw 'syntax "Day value is out of range"))
  (and hour
       (progn
	 (if (or (< hour 0)
                 (> hour 24)
                 (and (= hour 24)
                      (not (= minute 0))
                      (not (eq second 0))))
	     (throw 'syntax "Hour value is out of range"))
	 (if (or (< minute 0) (> minute 59))
	     (throw 'syntax "Minute value is out of range"))
	 (if (or (math-negp second) (not (Math-lessp second 60)))
	     (throw 'syntax "Seconds value is out of range"))))
  (list 'date (math-dt-to-date (append (list year month day)
				       (and hour (list hour minute second))))))

(defun math-parse-iso-date-validate (isoyear isoweek isoweekday hour minute second)
  (if (or (< isoweek 1) (> isoweek 53))
      (throw 'syntax "Week value is out of range"))
  (if (or (< isoweekday 1) (> isoweekday 7))
      (throw 'syntax "Weekday value is out of range"))
  (and hour
       (progn
	 (if (or (< hour 0)
                 (> hour 24)
                 (and (= hour 24)
                      (not (= minute 0))
                      (not (eq second 0))))
	     (throw 'syntax "Hour value is out of range"))
	 (if (or (< minute 0) (> minute 59))
	     (throw 'syntax "Minute value is out of range"))
	 (if (or (math-negp second) (not (Math-lessp second 60)))
	     (throw 'syntax "Seconds value is out of range"))))
  (list 'date (math-iso-dt-to-date (append (list isoyear isoweek isoweekday)
				       (and hour (list hour minute second))))))

(defun math-parse-date-word (names &optional front)
  (let ((n 1))
    (while (and names (not (string-match (if (equal (car names) "Sep")
					     "Sept?"
					   (regexp-quote (car names)))
					 math-pd-str)))
      (setq names (cdr names)
	    n (1+ n)))
    (and names
	 (or (not front) (= (match-beginning 0) 0))
	 (progn
	   (setq math-pd-str (concat (substring math-pd-str 0 (match-beginning 0))
			     (if front "" " ")
			     (substring math-pd-str (match-end 0))))
	   n))))

(defun math-parse-standard-date (math-pd-str with-time)
  (let ((case-fold-search t)
	(okay t) num
	(fmt calc-date-format) this next (gnext nil)
        (isoyear nil) (isoweek nil) (isoweekday nil)
	(year nil) (month nil) (day nil) (bigyear nil) (yearday nil)
	(hour nil) (minute nil) (second nil) (bc-flag nil))
    (while (and fmt okay)
      (setq this (car fmt)
	    fmt (setq fmt (or (cdr fmt)
				(prog1
				    gnext
				  (setq gnext nil))))
	    next (car fmt))
      (if (consp next) (setq next (car next)))
      (or (cond ((listp this)
		 (or (not with-time)
		     (not this)
		     (setq gnext fmt
			   fmt this)))
		((stringp this)
		 (if (and (<= (length this) (length math-pd-str))
			  (equal this
				 (substring math-pd-str 0 (length this))))
		     (setq math-pd-str (substring math-pd-str (length this)))))
		((eq this 'X)
		 t)
		((memq this '(n N j J))
		 (and (string-match "\\`[-+]?[0-9.]+\\([eE][-+]?[0-9]+\\)?" math-pd-str)
		      (setq num (math-match-substring math-pd-str 0)
			    math-pd-str (substring math-pd-str (match-end 0))
			    num (math-date-to-dt (math-read-number num))
			    num (math-sub num
					  (if (memq this '(n N))
					      0
					    (if (or (eq this 'j)
						    (math-integerp num))
                                                math-julian-date-beginning-int
                                              math-julian-date-beginning)))
			    hour (or (nth 3 num) hour)
			    minute (or (nth 4 num) minute)
			    second (or (nth 5 num) second)
			    year (car num)
			    month (nth 1 num)
			    day (nth 2 num))))
		((eq this 'U)
		 (and (string-match "\\`[-+]?[0-9]+" math-pd-str)
		      (setq num (math-match-substring math-pd-str 0)
			    math-pd-str (substring math-pd-str (match-end 0))
			    num (math-date-to-dt
				 (math-add 719164
					   (math-div (math-read-number num)
						     '(float 864 2))))
			    hour (nth 3 num)
			    minute (nth 4 num)
			    second (nth 5 num)
			    year (car num)
			    month (nth 1 num)
			    day (nth 2 num))))
		((memq this '(mmm Mmm MMM))
		 (setq month (math-parse-date-word math-short-month-names t)))
		((memq this '(Mmmm MMMM))
		 (setq month (math-parse-date-word math-long-month-names t)))
		((memq this '(www Www WWW))
		 (math-parse-date-word math-short-weekday-names t))
		((memq this '(Wwww WWWW))
		 (math-parse-date-word math-long-weekday-names t))
		((memq this '(p P))
		 (if (string-match "\\`a" math-pd-str)
		     (setq hour (if (= hour 12) 0 hour)
			   math-pd-str (substring math-pd-str 1))
		   (if (string-match "\\`p" math-pd-str)
		       (setq hour (if (= hour 12) 12 (% (+ hour 12) 24))
			     math-pd-str (substring math-pd-str 1)))))
		((memq this '(pp PP pppp PPPP))
		 (if (string-match "\\`am\\|a\\.m\\." math-pd-str)
		     (setq hour (if (= hour 12) 0 hour)
			   math-pd-str (substring math-pd-str (match-end 0)))
		   (if (string-match "\\`pm\\|p\\.m\\." math-pd-str)
		       (setq hour (if (= hour 12) 12 (% (+ hour 12) 24))
			     math-pd-str (substring math-pd-str (match-end 0))))))
		((memq this '(Y YY BY YYY YYYY ZYYY))
		 (and (if (memq next '(MM DD ddd hh HH mm ss SS))
			  (if (memq this '(Y YY BYY))
			      (string-match "\\` *[0-9][0-9]" math-pd-str)
			    (string-match "\\`[0-9][0-9][0-9][0-9]" math-pd-str))
			(string-match "\\`[-+]?[0-9]+" math-pd-str))
		      (setq year (math-match-substring math-pd-str 0)
                            bigyear (or (eq this 'YYY)
					(memq (aref math-pd-str 0) '(?\+ ?\-)))
			    math-pd-str (substring math-pd-str (match-end 0))
			    year (math-read-number year))
                      (if (and (eq this 'ZYYY) (eq year 0))
                          (setq year (math-sub year 1)
                                bigyear t)
                        t)))
		((eq this 'IYYY)
                 (if (string-match "\\`[-+]?[0-9]+" math-pd-str)
                     (setq isoyear (string-to-number (math-match-substring math-pd-str 0))
                           math-pd-str (substring math-pd-str (match-end 0)))))
                ((eq this 'Iww)
                 (if (string-match "W\\([0-9][0-9]\\)" math-pd-str)
                     (setq isoweek (string-to-number (math-match-substring math-pd-str 1))
                           math-pd-str (substring math-pd-str 3))))
		((eq this 'b)
		 t)
		((eq this 'T)
                 (if (eq (aref math-pd-str 0) ?T)
                     (setq math-pd-str (substring math-pd-str 1))
                   t))
		((memq this '(aa AA aaaa AAAA))
		 (if (string-match "\\` *\\(ad\\|a\\.d\\.\\)" math-pd-str)
		     (setq math-pd-str (substring math-pd-str (match-end 0)))))
		((memq this '(aaa AAA))
		 (if (string-match "\\` *ad *" math-pd-str)
		     (setq math-pd-str (substring math-pd-str (match-end 0)))))
		((memq this '(bb BB bbb BBB bbbb BBBB))
		 (if (string-match "\\` *\\(bc\\|b\\.c\\.\\)" math-pd-str)
		     (setq math-pd-str (substring math-pd-str (match-end 0))
			   bc-flag t)))
		((memq this '(s ss bs SS BS))
		 (and (if (memq next '(YY YYYY MM DD hh HH mm))
			  (string-match "\\` *[0-9][0-9]\\(\\.[0-9]+\\)?" math-pd-str)
			(string-match "\\` *[0-9][0-9]?\\(\\.[0-9]+\\)?" math-pd-str))
		      (setq second (math-match-substring math-pd-str 0)
			    math-pd-str (substring math-pd-str (match-end 0))
			    second (math-read-number second))))
		((eq this 'C)
		 (if (string-match "\\`:[0-9][0-9]" math-pd-str)
		     (setq math-pd-str (substring math-pd-str 1))
		   t))
		((or (not (if (and (memq this '(ddd MM DD hh HH mm))
				   (memq next '(YY YYYY MM DD ddd
						   hh HH mm ss SS)))
			      (if (eq this 'ddd)
				  (string-match "\\` *[0-9][0-9][0-9]" math-pd-str)
				(string-match "\\` *[0-9][0-9]" math-pd-str))
			    (string-match "\\` *[0-9]+" math-pd-str)))
		     (and (setq num (string-to-number
				     (math-match-substring math-pd-str 0))
				math-pd-str (substring math-pd-str (match-end 0)))
			  nil))
		 nil)
		((eq this 'W)
                 (and (>= num 0) (< num 7)))
                ((eq this 'w)
                 (setq isoweekday num))
		((memq this '(d ddd bdd))
		 (setq yearday num))
		((memq this '(M MM BM))
		 (setq month num))
		((memq this '(D DD BD))
		 (setq day num))
		((memq this '(h hh bh H HH BH))
		 (setq hour num))
		((memq this '(m mm bm))
		 (setq minute num)))
	  (setq okay nil)))
    (if yearday
	(if (and month day)
	    (setq yearday nil)
	  (setq month 1 day 1)))
    (if (and okay (equal math-pd-str ""))
        (if isoyear
            (math-parse-iso-date-validate isoyear isoweek isoweekday hour minute second)
          (and month day (or (not (or hour minute second))
                             (and hour minute))
               (progn
                 (or year (setq year (math-this-year)))
                 (or second (setq second 0))
                 (if bc-flag
                     (setq year (math-neg (math-abs year))))
                 (setq day (math-parse-date-validate year bigyear month day
                                                     hour minute second))
                 (if yearday
                     (setq day (math-add day (1- yearday))))
                 day))))))

(defun math-parse-iso-date (math-pd-str)
  "Parse MATH-PD-STR as an ISO week date, or return nil."
  (let ((case-fold-search t)
        (isoyear nil) (isoweek nil) (isoweekday nil)
        (hour nil) (minute nil) (second nil))
    ;; Extract the time, if any.
    (if (string-match "T[^0-9]*\\([0-9][0-9]\\)[^0-9]*\\([0-9][0-9]\\)?[^0-9]*\\([0-9][0-9]\\(\\.[0-9]+\\)?\\)?" math-pd-str)
        (progn
          (setq hour (string-to-number (math-match-substring math-pd-str 1))
                minute (math-match-substring math-pd-str 2)
                second (math-match-substring math-pd-str 3)
                math-pd-str (substring math-pd-str 0 (match-beginning 0)))
          (if (equal minute "")
              (setq minute 0)
            (setq minute (string-to-number minute)))
          (if (equal second "")
              (setq second 0)
            (setq second (math-read-number second)))))
    ;; Next, the year, week and weekday
    (if (string-match "\\(-?[0-9]*\\)[^0-9]*W\\([0-9][0-9]\\)[^0-9]*\\([0-9]\\)[^0-9]*\\'" math-pd-str)
        (progn
          (setq isoyear (string-to-number (math-match-substring math-pd-str 1))
                isoweek (string-to-number (math-match-substring math-pd-str 2))
                isoweekday (string-to-number (math-match-substring math-pd-str 3)))
          (math-parse-iso-date-validate isoyear isoweek isoweekday hour minute second)))))

(defun calcFunc-now (&optional zone)
  ;; FIXME: Support subseconds.
  (let ((date (let ((now (decode-time nil nil 'integer)))
		(list 'date (math-dt-to-date
			     (list (decoded-time-year now)
                                   (decoded-time-month now)
                                   (decoded-time-day now)
				   (decoded-time-hour now)
                                   (decoded-time-minute now)
                                   (decoded-time-second now)))))))
    (if zone
	(math-add date (math-div (math-sub (calcFunc-tzone nil date)
					   (calcFunc-tzone zone date))
				 '(float 864 2)))
      date)))

(defun calcFunc-year (date)
  (car (math-date-to-dt date)))

(defun calcFunc-month (date)
  (nth 1 (math-date-to-dt date)))

(defun calcFunc-day (date)
  (nth 2 (math-date-to-dt date)))

(defun calcFunc-weekday (date)
  (if (eq (car-safe date) 'date)
      (setq date (nth 1 date)))
  (or (math-realp date)
      (math-reject-arg date 'datep))
  (math-mod (math-floor date) 7))

(defun calcFunc-yearday (date)
  (let ((dt (math-date-to-dt date)))
    (math-day-number (car dt) (nth 1 dt) (nth 2 dt))))

(defun calcFunc-hour (date)
  (if (eq (car-safe date) 'hms)
      (nth 1 date)
    (or (nth 3 (math-date-to-dt date)) 0)))

(defun calcFunc-minute (date)
  (if (eq (car-safe date) 'hms)
      (nth 2 date)
    (or (nth 4 (math-date-to-dt date)) 0)))

(defun calcFunc-second (date)
  (if (eq (car-safe date) 'hms)
      (nth 3 date)
    (or (nth 5 (math-date-to-dt date)) 0)))

(defun calcFunc-time (date)
  (let ((dt (math-date-to-dt date)))
    (if (nth 3 dt)
	(cons 'hms (nthcdr 3 dt))
      (list 'hms 0 0 0))))

(defun calcFunc-date (date &optional month day hour minute second)
  (and (math-messy-integerp month) (setq month (math-trunc month)))
  (and month (not (integerp month)) (math-reject-arg month 'fixnump))
  (and (math-messy-integerp day) (setq day (math-trunc day)))
  (and day (not (integerp day)) (math-reject-arg day 'fixnump))
  (if (and (eq (car-safe hour) 'hms) (not minute))
      (setq second (nth 3 hour)
	    minute (nth 2 hour)
	    hour (nth 1 hour)))
  (and (math-messy-integerp hour) (setq hour (math-trunc hour)))
  (and hour (not (integerp hour)) (math-reject-arg hour 'fixnump))
  (and (math-messy-integerp minute) (setq minute (math-trunc minute)))
  (and minute (not (integerp minute)) (math-reject-arg minute 'fixnump))
  (and (math-messy-integerp second) (setq second (math-trunc second)))
  (and second (not (math-realp second)) (math-reject-arg second 'realp))
  (if month
      (progn
	(and (math-messy-integerp date) (setq date (math-trunc date)))
	(and date (not (math-integerp date)) (math-reject-arg date 'integerp))
	(if day
	    (if hour
		(list 'date (math-dt-to-date (list date month day hour
						   (or minute 0)
						   (or second 0))))
	      (list 'date (math-dt-to-date (list date month day))))
	  (list 'date (math-dt-to-date (list (math-this-year) date month)))))
    (if (math-realp date)
	(list 'date date)
      (if (eq (car date) 'date)
	  (nth 1 date)
	(math-reject-arg date 'datep)))))

(defun calcFunc-julian (date &optional zone)
  (if (math-realp date)
      (list 'date (if (math-integerp date)
		      (math-sub date math-julian-date-beginning-int)
		    (setq date (math-sub date math-julian-date-beginning))
		    (math-sub date (math-div (calcFunc-tzone zone date)
					     '(float 864 2)))))
    (if (eq (car date) 'date)
	(math-add (nth 1 date) (if (math-integerp (nth 1 date))
                                   math-julian-date-beginning-int
				 (math-add math-julian-date-beginning
					   (math-div (calcFunc-tzone zone date)
						     '(float 864 2)))))
      (math-reject-arg date 'datep))))

(defun calcFunc-unixtime (date &optional zone)
  (if (math-realp date)
      (progn
	(setq date (math-add 719163 (math-div date '(float 864 2))))
	(list 'date (math-sub date (math-div (calcFunc-tzone zone date)
					     '(float 864 2)))))
    (if (eq (car date) 'date)
	(math-add (nth 1 (math-date-parts (nth 1 date) 719163))
		  (calcFunc-tzone zone date))
      (math-reject-arg date 'datep))))


;;; Note: Longer names must appear before shorter names which are
;;;       substrings of them.
(defvar math-tzone-names
  '(( "UTC" 0 0)
    ( "MEGT" -1 "MET" "METDST" )                          ; Middle Europe
    ( "METDST" -1 -1 ) ( "MET" -1 0 )
    ( "MEGZ" -1 "MEZ" "MESZ" ) ( "MEZ" -1 0 ) ( "MESZ" -1 -1 )
    ( "WEGT" 0 "WET" "WETDST" )                           ; Western Europe
    ( "WETDST" 0 -1 ) ( "WET" 0 0 )
    ( "BGT" 0 "GMT" "BST" ) ( "GMT" 0 0 ) ( "BST" 0 -1 )  ; Britain
    ( "NGT" (float 35 -1) "NST" "NDT" )                   ; Newfoundland
    ( "NST" (float 35 -1) 0 ) ( "NDT" (float 35 -1) -1 )
    ( "AGT" 4 "AST" "ADT" ) ( "AST" 4 0 ) ( "ADT" 4 -1 )  ; Atlantic
    ( "EGT" 5 "EST" "EDT" ) ( "EST" 5 0 ) ( "EDT" 5 -1 )  ; Eastern
    ( "CGT" 6 "CST" "CDT" ) ( "CST" 6 0 ) ( "CDT" 6 -1 )  ; Central
    ( "MGT" 7 "MST" "MDT" ) ( "MST" 7 0 ) ( "MDT" 7 -1 )  ; Mountain
    ( "PGT" 8 "PST" "PDT" ) ( "PST" 8 0 ) ( "PDT" 8 -1 )  ; Pacific
    ( "YGT" 9 "YST" "YDT" ) ( "YST" 9 0 ) ( "YDT" 9 -1 )  ; Yukon
    )
  "No doc yet.  See calc manual for now.")

(defvar var-TimeZone nil)

(defvar math-calendar-tzinfo
  nil
  "Information about the timezone, retrieved from the calendar.")

(defun math-get-calendar-tzinfo ()
  "Get information about the timezone from the calendar.
The result should be a list of two items about the current time zone:
first, the number of seconds difference from GMT
second, the number of seconds offset for daylight savings."
  (if math-calendar-tzinfo
      math-calendar-tzinfo
    (require 'cal-dst)
    (let ((tzinfo (calendar-current-time-zone)))
      (setq math-calendar-tzinfo
            (list (* 60 (- (nth 0 tzinfo)))
                  (* 60 (nth 1 tzinfo)))))))

(defun calcFunc-tzone (&optional zone date)
  (if zone
      (cond ((math-realp zone)
	     (math-round (math-mul zone 3600)))
	    ((eq (car zone) 'hms)
	     (math-round (math-mul (math-from-hms zone 'deg) 3600)))
	    ((eq (car zone) '+)
	     (math-add (calcFunc-tzone (nth 1 zone) date)
		       (calcFunc-tzone (nth 2 zone) date)))
	    ((eq (car zone) '-)
	     (math-sub (calcFunc-tzone (nth 1 zone) date)
		       (calcFunc-tzone (nth 2 zone) date)))
	    ((eq (car zone) 'var)
	     (let ((name (upcase (symbol-name (nth 1 zone))))
		   found)
	       (if (setq found (assoc name math-tzone-names))
		   (calcFunc-tzone (math-add (nth 1 found)
					     (if (integerp (nth 2 found))
						 (nth 2 found)
					       (or
						(math-daylight-savings-adjust
						 date (car found))
						0)))
				   date)
		 (if (equal name "LOCAL")
		     (calcFunc-tzone nil date)
		   (math-reject-arg zone "*Unrecognized time zone name")))))
	    (t (math-reject-arg zone "*Expected a time zone")))
    (if (calc-var-value 'var-TimeZone)
	(calcFunc-tzone (calc-var-value 'var-TimeZone) date)
      (let ((tzinfo (math-get-calendar-tzinfo)))
        (+ (nth 0 tzinfo)
           (* (math-cal-daylight-savings-adjust date) (nth 1 tzinfo)))))))

(defvar math-daylight-savings-hook 'math-std-daylight-savings)

(defun math-daylight-savings-adjust (date zone &optional dt)
  (or date (setq date (nth 1 (calcFunc-now))))
  (let (bump)
    (if (eq (car-safe date) 'date)
	(setq bump 0
	      date (nth 1 date))
      (if (and date (math-realp date))
	  (let ((zadj (assoc zone math-tzone-names)))
	    (if zadj (setq bump -1
			   date (math-sub date (math-div (nth 1 zadj)
							 '(float 24 0))))))
	(math-reject-arg date 'datep)))
    (setq date (math-float date))
    (or dt (setq dt (math-date-to-dt date)))
    (and math-daylight-savings-hook
	 (funcall math-daylight-savings-hook date dt zone bump))))

;;; Based on part of dst-adjust-time in cal-dst.el
;;; For calcFunc-dst, when zone=nil
(defun math-cal-daylight-savings-adjust (date)
  "Return -1 if DATE is using daylight saving, 0 otherwise."
  (require 'cal-dst)
  (unless date (setq date (calcFunc-now)))
  (let* ((dt (math-date-to-dt date))
         (time (cond
                ((nth 3 dt)
                 (nth 3 dt))
                ((nth 4 dt)
                 (+ (nth 3 dt) (/ (nth 4 dt) 60.0)))
                (t
                 0)))
         (rounded-abs-date
          (+
           (calendar-absolute-from-gregorian
            (list (nth 1 dt) (nth 2 dt) (nth 0 dt)))
           (/ (round (* 60 time)) 60.0 24.0))))
    (if (dst-in-effect rounded-abs-date)
        -1
      0)))

(defun calcFunc-dsadj (date &optional zone)
  (if zone
      (or (eq (car-safe zone) 'var)
	  (math-reject-arg zone "*Time zone variable expected"))
    (setq zone (calc-var-value 'var-TimeZone)))
  (if zone
      (progn
        (setq zone (and (eq (car-safe zone) 'var)
                        (upcase (symbol-name (nth 1 zone)))))
        (let ((zadj (assoc zone math-tzone-names)))
          (or zadj (math-reject-arg zone "*Unrecognized time zone name"))
          (if (integerp (nth 2 zadj))
              (nth 2 zadj)
            (math-daylight-savings-adjust date zone))))
    (math-cal-daylight-savings-adjust date)))

;; (defun calcFunc-dsadj (date &optional zone)
;;   (if zone
;;       (or (eq (car-safe zone) 'var)
;; 	  (math-reject-arg zone "*Time zone variable expected"))
;;     (setq zone (or (calc-var-value 'var-TimeZone)
;; 		   (progn
;; 		     (calcFunc-tzone)
;; 		     (calc-var-value 'var-TimeZone)))))
;;   (setq zone (and (eq (car-safe zone) 'var)
;; 		  (upcase (symbol-name (nth 1 zone)))))
;;   (let ((zadj (assoc zone math-tzone-names)))
;;     (or zadj (math-reject-arg zone "*Unrecognized time zone name"))
;;     (if (integerp (nth 2 zadj))
;; 	(nth 2 zadj)
;;       (math-daylight-savings-adjust date zone))))

(defun calcFunc-tzconv (date z1 z2)
  (if (math-realp date)
      (nth 1 (calcFunc-tzconv (list 'date date) z1 z2))
    (calcFunc-unixtime (calcFunc-unixtime date z1) z2)))

(defun math-std-daylight-savings (date dt zone bump)
  "Standard North American daylight saving algorithm.
Before 2007, this uses `math-std-daylight-savings-old', where
daylight saving began on the first Sunday of April at 2 a.m.,
and ended on the last Sunday of October at 2 a.m.
As of 2007, this uses `math-std-daylight-savings-new', where
daylight saving begins on the second Sunday of March at 2 a.m.,
and ends on the first Sunday of November at 2 a.m."
  (if (< (car dt) 2007)
      (math-std-daylight-savings-old date dt zone bump)
    (math-std-daylight-savings-new date dt zone bump)))

(defun math-std-daylight-savings-new (date dt zone bump)
  "Standard North American daylight saving algorithm as of 2007.
This implements the rules for the U.S. and Canada.
Daylight saving begins on the second Sunday of March at 2 a.m.,
and ends on the first Sunday of November at 2 a.m."
  (cond ((< (nth 1 dt) 3) 0)
	((= (nth 1 dt) 3)
	 (let ((sunday (math-prev-weekday-in-month date dt 14 0)))
	   (cond ((< (nth 2 dt) sunday) 0)
		 ((= (nth 2 dt) sunday)
		  (if (>= (nth 3 dt) (+ 3 bump)) -1 0))
		 (t -1))))
	((< (nth 1 dt) 11) -1)
	((= (nth 1 dt) 11)
	 (let ((sunday (math-prev-weekday-in-month date dt 7 0)))
	   (cond ((< (nth 2 dt) sunday) -1)
		 ((= (nth 2 dt) sunday)
		  (if (>= (nth 3 dt) (+ 2 bump)) 0 -1))
		 (t 0))))
	(t 0)))

(defun math-std-daylight-savings-old (date dt zone bump)
  "Standard North American daylight saving algorithm before 2007.
This implements the rules for the U.S. and Canada.
Daylight saving begins on the first Sunday of April at 2 a.m.,
and ends on the last Sunday of October at 2 a.m."
  (cond ((< (nth 1 dt) 4) 0)
	((= (nth 1 dt) 4)
	 (let ((sunday (math-prev-weekday-in-month date dt 7 0)))
	   (cond ((< (nth 2 dt) sunday) 0)
		 ((= (nth 2 dt) sunday)
		  (if (>= (nth 3 dt) (+ 3 bump)) -1 0))
		 (t -1))))
	((< (nth 1 dt) 10) -1)
	((= (nth 1 dt) 10)
	 (let ((sunday (math-prev-weekday-in-month date dt 31 0)))
	   (cond ((< (nth 2 dt) sunday) -1)
		 ((= (nth 2 dt) sunday)
		  (if (>= (nth 3 dt) (+ 2 bump)) 0 -1))
		 (t 0))))
	(t 0)))

;;; Compute the day (1-31) of the WDAY (0-6) on or preceding the given
;;; day of the given month.
(defun math-prev-weekday-in-month (date dt day wday)
  (or day (setq day (nth 2 dt)))
  (if (> day (math-days-in-month (car dt) (nth 1 dt)))
      (setq day (math-days-in-month (car dt) (nth 1 dt))))
  (let ((zeroth (math-sub (math-floor date) (nth 2 dt))))
    (math-sub (nth 1 (calcFunc-newweek (math-add zeroth day))) zeroth)))

(defun calcFunc-pwday (date &optional day weekday)
  (if (eq (car-safe date) 'date)
      (setq date (nth 1 date)))
  (or (math-realp date)
      (math-reject-arg date 'datep))
  (if (math-messy-integerp day) (setq day (math-trunc day)))
  (or (integerp day) (math-reject-arg day 'fixnump))
  (if (= day 0) (setq day 31))
  (and (or (< day 7) (> day 31)) (math-reject-arg day 'range))
  (math-prev-weekday-in-month date (math-date-to-dt date) day (or weekday 0)))


(defun calcFunc-newweek (date &optional weekday)
  (if (eq (car-safe date) 'date)
      (setq date (nth 1 date)))
  (or (math-realp date)
      (math-reject-arg date 'datep))
  (or weekday (setq weekday 0))
  (and (math-messy-integerp weekday) (setq weekday (math-trunc weekday)))
  (or (integerp weekday) (math-reject-arg weekday 'fixnump))
  (and (or (< weekday 0) (> weekday 6)) (math-reject-arg weekday 'range))
  (setq date (math-floor date))
  (list 'date (math-sub date (calcFunc-weekday (math-sub date weekday)))))

(defun calcFunc-newmonth (date &optional day)
  (or day (setq day 1))
  (and (math-messy-integerp day) (setq day (math-trunc day)))
  (or (integerp day) (math-reject-arg day 'fixnump))
  (and (or (< day 0) (> day 31)) (math-reject-arg day 'range))
  (let* ((dt (math-date-to-dt date))
         (dim (math-days-in-month (car dt) (nth 1 dt)))
         (julian (if calc-gregorian-switch
                     (math-date-to-dt (math-sub
                                       (or (nth 3 calc-gregorian-switch)
                                           (apply 'math-absolute-from-gregorian-dt calc-gregorian-switch))
                                       1)))))
    (if (or (= day 0) (> day dim))
	(setq day (1- dim))
      (setq day (1- day)))
    ;; Adjust if this occurs near the switch to the Gregorian calendar
    (if calc-gregorian-switch
        (cond
         ((and (math-dt-before-p (list (car dt) (nth 1 dt) 1) calc-gregorian-switch)
               (math-dt-before-p julian (list (car dt) (nth 1 dt) 1)))
          ;; In this case, CALC-GREGORIAN-SWITCH is the first day of the month
          (list 'date
                (math-dt-to-date (list (car calc-gregorian-switch)
                                       (nth 1 calc-gregorian-switch)
                                       (if (> (+ (nth 2 calc-gregorian-switch) day) dim)
                                           dim
                                         (+ (nth 2 calc-gregorian-switch) day))))))
         ((and (eq (car dt) (car calc-gregorian-switch))
               (= (nth 1 dt) (nth 1 calc-gregorian-switch)))
          ;; In this case, the switch to the Gregorian calendar occurs in the given month
          (if (< (+ (nth 2 julian) day) (nth 2 calc-gregorian-switch))
              ;; If the DAYth day occurs before the switch, use it
              (list 'date (math-dt-to-date (list (car dt) (nth 1 dt) (1+ day))))
            ;; Otherwise do some computations
            (let ((tm (+ day (- (nth 2 calc-gregorian-switch) (nth 2 julian)))))
              (list 'date (math-dt-to-date
                           (list (car dt)
                                 (nth 1 dt)
                                 ;;
                                 (if (> tm dim) dim tm)))))))
         ((and (eq (car dt) (car julian))
               (= (nth 1 dt) (nth 1 julian)))
          ;; In this case, the current month is truncated because of the switch
          ;; to the Gregorian calendar
          (list 'date (math-dt-to-date
                       (list (car dt)
                             (nth 1 dt)
                             (if (>= day (nth 2 julian))
                                 (nth 2 julian)
                               (1+ day))))))
         (t
          ;; The default
          (list 'date (math-add (math-dt-to-date (list (car dt) (nth 1 dt) 1)) day))))
      (list 'date (math-add (math-dt-to-date (list (car dt) (nth 1 dt) 1)) day)))))

(defun calcFunc-newyear (date &optional day)
  (if (eq (car-safe date) 'date) (setq date (nth 1 date)))
  (or day (setq day 1))
  (and (math-messy-integerp day) (setq day (math-trunc day)))
  (or (integerp day) (math-reject-arg day 'fixnump))
  (let* ((dt (math-date-to-dt date))
         (gregbeg (if calc-gregorian-switch
                      (or (nth 3 calc-gregorian-switch)
                          (apply 'math-absolute-from-gregorian-dt calc-gregorian-switch))))
         (julianend (if calc-gregorian-switch (math-sub gregbeg 1)))
         (julian (if calc-gregorian-switch
                     (math-date-to-dt julianend))))
    (if (and (>= day 0) (<= day 366))
	(let ((max (if (math-leap-year-p (car dt)) 366 365)))
	  (if (or (= day 0) (> day max)) (setq day max))
          (if calc-gregorian-switch
              ;; Now to break this down into cases
              (cond
               ((and (math-dt-before-p (list (car dt) 1 1) calc-gregorian-switch)
                     (math-dt-before-p julian (list (car dt) 1 1)))
                ;; In this case, CALC-GREGORIAN-SWITCH is the first day of the year
                (list 'date (math-min (math-add gregbeg (1- day))
                                      (math-dt-to-date (list (car calc-gregorian-switch) 12 31)))))
               ((eq (car dt) (car julian))
                ;; In this case, the switch to the Gregorian calendar occurs in the given year
                (if (Math-lessp (car julian) (car calc-gregorian-switch))
                    ;; Here, the last Julian day is the last day of the year.
                    (list 'date (math-min (math-add (math-dt-to-date (list (car dt) 1 1)) (1- day))
                                          julianend))
                  ;; Otherwise, just make sure the date doesn't go past the end of the year
                  (list 'date (math-min (math-add (math-dt-to-date (list (car dt) 1 1)) (1- day))
                                        (math-dt-to-date (list (car dt) 12 31))))))
               (t
                (list 'date (math-add (math-dt-to-date (list (car dt) 1 1))
                                      (1- day)))))
            (list 'date (math-add (math-dt-to-date (list (car dt) 1 1))
                                  (1- day)))))
      (if (and (>= day -12) (<= day -1))
          (if (and calc-gregorian-switch
                   (math-dt-before-p (list (car dt) (- day) 1) calc-gregorian-switch)
                   (math-dt-before-p julian (list (car dt) (- day) 1)))
              (list 'date gregbeg)
            (list 'date (math-dt-to-date (list (car dt) (- day) 1))))
        (math-reject-arg day 'range)))))

(defun calcFunc-incmonth (date &optional step)
  (or step (setq step 1))
  (and (math-messy-integerp step) (setq step (math-trunc step)))
  (or (math-integerp step) (math-reject-arg step 'integerp))
  (let* ((dt (math-date-to-dt date))
	 (year (car dt))
	 (month (math-add (1- (nth 1 dt)) step))
	 (extra (calcFunc-idiv month 12))
	 (day (nth 2 dt)))
    (setq month (1+ (math-sub month (math-mul extra 12)))
	  year (math-add year extra)
	  day (min day (math-days-in-month year month)))
    (and (math-posp (car dt)) (not (math-posp year))
	 (setq year (math-sub year 1)))   ; did we go past the year zero?
    (and (math-negp (car dt)) (not (math-negp year))
	 (setq year (math-add year 1)))
    (list 'date (math-dt-to-date
		 (cons year (cons month (cons day (cdr (cdr (cdr dt))))))))))

(defun calcFunc-incyear (date &optional step)
  (calcFunc-incmonth date (math-mul (or step 1) 12)))



(defun calcFunc-bsub (a b)
  (or (eq (car-safe a) 'date)
      (math-reject-arg a 'datep))
  (if (eq (car-safe b) 'date)
      (if (math-lessp (nth 1 a) (nth 1 b))
	  (math-neg (calcFunc-bsub b a))
	(math-setup-holidays b)
	(let* ((da (math-to-business-day a))
	       (db (math-to-business-day b)))
	  (math-add (math-sub (car da) (car db))
		    (if (and (cdr db) (not (cdr da))) 1 0))))
    (calcFunc-badd a (math-neg b))))

(defvar math-holidays-cache nil)
(defvar math-holidays-cache-tag t)
(defun calcFunc-badd (a b)
  (if (eq (car-safe b) 'date)
      (if (eq (car-safe a) 'date)
	  (math-reject-arg nil "*Invalid combination in date arithmetic")
	(calcFunc-badd b a))
    (if (eq (car-safe a) 'date)
	(if (Math-realp b)
	    (if (Math-zerop b)
		a
	      (let* ((d (math-to-business-day a))
		     (bb (math-add (car d)
				   (if (and (cdr d) (Math-posp b))
				       (math-sub b 1) b))))
		(or (math-from-business-day bb)
		    (calcFunc-badd a b))))
	  (if (eq (car-safe b) 'hms)
	      (let ((hours (nth 7 math-holidays-cache)))
		(setq b (math-div (math-from-hms b 'deg) 24))
		(if hours
		    (setq b (math-div b (cdr hours))))
		(calcFunc-badd a b))
	    (math-reject-arg nil "*Invalid combination in date arithmetic")))
      (math-reject-arg a 'datep))))

(defun calcFunc-holiday (a)
  (if (cdr (math-to-business-day a)) 1 0))

;;; Compute the number of business days since Jan 1, 1 AD.

(defun math-to-business-day (date &optional need-year)
  (if (eq (car-safe date) 'date)
      (setq date (nth 1 date)))
  (or (Math-realp date)
      (math-reject-arg date 'datep))
  (let* ((day (math-floor date))
	 (time (math-sub date day))
	 (dt (math-date-to-dt day))
	 (delta 0)
	 (holiday nil))
    (or (not need-year) (eq (car dt) need-year)
	(math-reject-arg (list 'date day) "*Generated holiday has wrong year"))
    (math-setup-holidays date)
    (let ((days (car math-holidays-cache)))
      (while (and (setq days (cdr days)) (< (car days) day))
	(setq delta (1+ delta)))
      (and days (= day (car days))
	   (setq holiday t)))
    (let* ((weekdays (nth 3 math-holidays-cache))
	   (weeks (1- (/ (+ day 6) 7)))
	   (wkday (- day 1 (* weeks 7))))
      (setq delta (+ delta (* weeks (length weekdays))))
      (while (and weekdays (< (car weekdays) wkday))
	(setq weekdays (cdr weekdays)
	      delta (1+ delta)))
      (and weekdays (eq wkday (car weekdays))
	   (setq holiday t)))
    (let ((hours (nth 7 math-holidays-cache)))
      (if hours
	  (progn
	    (setq time (math-div (math-sub time (car hours)) (cdr hours)))
	    (if (Math-lessp time 0) (setq time 0))
	    (or (Math-lessp time 1)
		(setq time
		      (math-sub 1
				(math-div 1 (math-mul 86400 (cdr hours)))))))))
    (cons (math-add (math-sub day delta) time) holiday)))


;;; Compute the date a certain number of business days since Jan 1, 1 AD.
;;; If this returns nil, holiday table was adjusted; redo calculation.

(defun math-from-business-day (num)
  (let* ((day (math-floor num))
	 (time (math-sub num day)))
    (or (integerp day)
	(math-reject-arg nil "*Date is outside valid range"))
    (math-setup-holidays)
    (let ((days (nth 1 math-holidays-cache))
	  (delta 0))
      (while (and (setq days (cdr days)) (< (car days) day))
	(setq delta (1+ delta)))
      (setq day (+ day delta)))
    (let* ((weekdays (nth 3 math-holidays-cache))
	   (bweek (- 7 (length weekdays)))
	   (weeks (1- (/ (+ day (1- bweek)) bweek)))
	   (wkday (- day 1 (* weeks bweek)))
	   (w 0))
      (setq day (+ day (* weeks (length weekdays))))
      (while (if (memq w weekdays)
		 (setq day (1+ day))
	       (> (setq wkday (1- wkday)) 0))
	(setq w (1+ w)))
      (let ((hours (nth 7 math-holidays-cache)))
	(if hours
	    (setq time (math-add (math-mul time (cdr hours)) (car hours)))))
      (and (not (math-setup-holidays day))
	   (list 'date (math-add day time))))))

;; The variable math-sh-year is local to math-setup-holidays
;; and math-setup-year-holiday, but is used by math-setup-add-holidays,
;; which is called by math-setup-holidays and math-setup-year-holiday.
(defvar math-sh-year)

(defun math-setup-holidays (&optional date)
  (or (eq (calc-var-value 'var-Holidays) math-holidays-cache-tag)
      (let ((h (calc-var-value 'var-Holidays))
	    (wdnames '( (mon . 0) (tue . 1) (wed . 2)
			(thu . 3) (fri . 4) (sat . 5) (sun . 6) ))
	    (days nil) (weekdays nil) (exprs nil) (limit nil) (hours nil))
	(or (math-vectorp h)
	    (math-reject-arg h "*Holidays variable must be a vector"))
	(while (setq h (cdr h))
	  (cond ((or (and (eq (car-safe (car h)) 'date)
			  (integerp (nth 1 (car h))))
		     (and (eq (car-safe (car h)) 'intv)
			  (eq (car-safe (nth 2 (car h))) 'date))
		     (eq (car-safe (car h)) 'vec))
		 (setq days (cons (car h) days)))
		((and (eq (car-safe (car h)) 'var)
		      (assq (nth 1 (car h)) wdnames))
		 (setq weekdays (cons (cdr (assq (nth 1 (car h)) wdnames))
				      weekdays)))
		((and (eq (car-safe (car h)) 'intv)
		      (eq (car-safe (nth 2 (car h))) 'hms)
		      (eq (car-safe (nth 3 (car h))) 'hms))
		 (if hours
		     (math-reject-arg
		      (car h) "*Only one hours interval allowed in Holidays"))
		 (setq hours (math-div (car h) '(hms 24 0 0)))
		 (if (or (Math-lessp (nth 2 hours) 0)
			 (Math-lessp 1 (nth 3 hours)))
		     (math-reject-arg
		      (car h) "*Hours interval out of range"))
		 (setq hours (cons (nth 2 hours)
				   (math-sub (nth 3 hours) (nth 2 hours))))
		 (if (Math-zerop (cdr hours))
		     (math-reject-arg
		      (car h) "*Degenerate hours interval")))
		((or (and (eq (car-safe (car h)) 'intv)
			  (Math-integerp (nth 2 (car h)))
			  (Math-integerp (nth 3 (car h))))
		     (and (integerp (car h))
			  (> (car h) 1900) (< (car h) 2100)))
		 (if limit
		     (math-reject-arg
		      (car h) "*Only one limit allowed in Holidays"))
		 (setq limit (calcFunc-vint (car h) '(intv 3 1 2737)))
		 (if (equal limit '(vec))
		     (math-reject-arg (car h) "*Limit is out of range")))
		((or (math-expr-contains (car h) '(var y var-y))
		     (math-expr-contains (car h) '(var m var-m)))
		 (setq exprs (cons (car h) exprs)))
		(t (math-reject-arg
		    (car h) "*Holidays must contain a vector of holidays"))))
	(if (= (length weekdays) 7)
	    (math-reject-arg nil "*Too many weekend days"))
	(setq math-holidays-cache (list (list -1)  ; 0: days list
					(list -1)  ; 1: inverse-days list
					nil        ; 2: exprs
					(sort weekdays '<)
					(or limit '(intv 3 1 2737))
					nil        ; 5: (lo.hi) expanded years
					(cons exprs days)
					hours)     ; 7: business hours
	      math-holidays-cache-tag (calc-var-value 'var-Holidays))))
  (if date
      (let ((year (calcFunc-year date))
	    (limits (nth 5 math-holidays-cache))
	    (done nil))
	(or (eq (calcFunc-in year (nth 4 math-holidays-cache)) 1)
	    (progn
	      (or (eq (car-safe date) 'date) (setq date (list 'date date)))
	      (math-reject-arg date "*Date is outside valid range")))
	(unwind-protect
	    (let ((days (nth 6 math-holidays-cache)))
	      (if days
		  (let ((math-sh-year nil))   ; see below
		    (setcar (nthcdr 6 math-holidays-cache) nil)
		    (math-setup-add-holidays (cons 'vec (cdr days)))
		    (setcar (nthcdr 2 math-holidays-cache) (car days))))
	      (cond ((not (nth 2 math-holidays-cache))
		     (setq done t)
		     nil)
		    ((not limits)
		     (setcar (nthcdr 5 math-holidays-cache) (cons year year))
		     (math-setup-year-holidays year)
		     (setq done t))
		    ((< year (car limits))
		     (message "Computing holidays, %d .. %d"
			      year (1- (car limits)))
		     (calc-set-command-flag 'clear-message)
		     (while (< year (car limits))
		       (setcar limits (1- (car limits)))
		       (math-setup-year-holidays (car limits)))
		     (setq done t))
		    ((> year (cdr limits))
		     (message "Computing holidays, %d .. %d"
			      (1+ (cdr limits)) year)
		     (calc-set-command-flag 'clear-message)
		     (while (> year (cdr limits))
		       (setcdr limits (1+ (cdr limits)))
		       (math-setup-year-holidays (cdr limits)))
		     (setq done t))
		    (t
		     (setq done t)
		     nil)))
	  (or done (setq math-holidays-cache-tag t))))))

(defun math-setup-year-holidays (math-sh-year)
  (let ((exprs (nth 2 math-holidays-cache)))
    (while exprs
      (let* ((var-y math-sh-year)
	     (var-m nil)
	     (expr (math-evaluate-expr (car exprs))))
	(if (math-expr-contains expr '(var m var-m))
	    (let ((var-m 0))
	      (while (<= (setq var-m (1+ var-m)) 12)
		(math-setup-add-holidays (math-evaluate-expr expr))))
	  (math-setup-add-holidays expr)))
      (setq exprs (cdr exprs)))))

(defun math-setup-add-holidays (days)   ; uses "math-sh-year"
  (cond ((eq (car-safe days) 'vec)
	 (while (setq days (cdr days))
	   (math-setup-add-holidays (car days))))
	((eq (car-safe days) 'intv)
	 (let ((day (math-ceiling (nth 2 days))))
	   (or (eq (calcFunc-in day days) 1)
	       (setq day (math-add day 1)))
	   (while (eq (calcFunc-in day days) 1)
	     (math-setup-add-holidays day)
	     (setq day (math-add day 1)))))
	((eq (car-safe days) 'date)
	 (math-setup-add-holidays (nth 1 days)))
	((eq days 0))
	((integerp days)
	 (let ((b (math-to-business-day days math-sh-year)))
	   (or (cdr b)   ; don't register holidays twice!
	       (let ((prev (car math-holidays-cache))
		     (iprev (nth 1 math-holidays-cache)))
		 (while (and (cdr prev) (< (nth 1 prev) days))
		   (setq prev (cdr prev) iprev (cdr iprev)))
		 (setcdr prev (cons days (cdr prev)))
		 (setcdr iprev (cons (car b) (cdr iprev)))
		 (while (setq iprev (cdr iprev))
		   (setcar iprev (1- (car iprev))))))))
	((Math-realp days)
	 (math-reject-arg (list 'date days) "*Invalid holiday value"))
	(t
	 (math-reject-arg days "*Holiday formula failed to evaluate"))))




;;;; Error forms.

;;; Build a standard deviation form.  [X X X]
(defun math-make-sdev (x sigma)
  (if (memq (car-safe x) '(date mod sdev intv vec))
      (math-reject-arg x 'realp))
  (if (memq (car-safe sigma) '(date mod sdev intv vec))
      (math-reject-arg sigma 'realp))
  (if (or (Math-negp sigma) (memq (car-safe sigma) '(cplx polar)))
      (setq sigma (math-abs sigma)))
  (if (and (Math-zerop sigma) (Math-scalarp x))
      x
    (list 'sdev x sigma)))
(defun calcFunc-sdev (x sigma)
  (math-make-sdev x sigma))



;;;; Modulo forms.

(defun math-normalize-mod (a)
  (let ((n (math-normalize (nth 1 a)))
	(m (math-normalize (nth 2 a))))
    (if (and (math-anglep n) (math-anglep m) (math-posp m))
	(math-make-mod n m)
      (math-normalize (list 'calcFunc-makemod n m)))))

;;; Build a modulo form.  [N R R]
(defun math-make-mod (n m)
  (setq calc-previous-modulo m)
  (and n
       (cond ((not (Math-anglep m))
	      (math-reject-arg m 'anglep))
	     ((not (math-posp m))
	      (math-reject-arg m 'posp))
	     ((Math-anglep n)
	      (if (or (Math-negp n)
		      (not (Math-lessp n m)))
		  (list 'mod (math-mod n m) m)
		(list 'mod n m)))
	     ((memq (car n) '(+ - / vec neg))
	      (math-normalize
	       (cons (car n)
		     (mapcar (function (lambda (x) (math-make-mod x m)))
			     (cdr n)))))
	     ((and (eq (car n) '*) (Math-anglep (nth 1 n)))
	      (math-mul (math-make-mod (nth 1 n) m) (nth 2 n)))
	     ((memq (car n) '(* ^ var calcFunc-subscr))
	      (math-mul (math-make-mod 1 m) n))
	     (t (math-reject-arg n 'anglep)))))
(defun calcFunc-makemod (n m)
  (math-make-mod n m))



;;;; Interval forms.

;;; Build an interval form.  [X S X X]
(defun math-make-intv (mask lo hi)
  (if (memq (car-safe lo) '(cplx polar mod sdev intv vec))
      (math-reject-arg lo 'realp))
  (if (memq (car-safe hi) '(cplx polar mod sdev intv vec))
      (math-reject-arg hi 'realp))
  (or (eq (eq (car-safe lo) 'date) (eq (car-safe hi) 'date))
      (math-reject-arg (if (eq (car-safe lo) 'date) hi lo) 'datep))
  (if (and (or (Math-realp lo) (eq (car lo) 'date))
	   (or (Math-realp hi) (eq (car hi) 'date)))
      (let ((cmp (math-compare lo hi)))
	(if (= cmp 0)
	    (if (= mask 3)
		lo
	      (list 'intv mask lo hi))
	  (if (> cmp 0)
	      (if (= mask 3)
		  (list 'intv 2 lo lo)
		(list 'intv mask lo lo))
	    (list 'intv mask lo hi))))
    (list 'intv mask lo hi)))
(defun calcFunc-intv (mask lo hi)
  (if (math-messy-integerp mask) (setq mask (math-trunc mask)))
  (or (natnump mask) (math-reject-arg mask 'fixnatnump))
  (or (<= mask 3) (math-reject-arg mask 'range))
  (math-make-intv mask lo hi))

(defun math-sort-intv (mask lo hi)
  (if (Math-lessp hi lo)
      (math-make-intv (aref [0 2 1 3] mask) hi lo)
    (math-make-intv mask lo hi)))




(defun math-combine-intervals (a am b bm c cm d dm)
  (let (res)
    (if (= (setq res (math-compare a c)) 1)
	(setq a c am cm)
      (if (= res 0)
	  (setq am (or am cm))))
    (if (= (setq res (math-compare b d)) -1)
	(setq b d bm dm)
      (if (= res 0)
	  (setq bm (or bm dm))))
    (math-make-intv (+ (if am 2 0) (if bm 1 0)) a b)))


(defun math-div-mod (a b m)   ; [R R R R]  (Returns nil if no solution)
  (and (Math-integerp a) (Math-integerp b) (Math-integerp m)
       (let ((u1 1) (u3 b) (v1 0) (v3 m))
	 (while (not (eq v3 0))   ; See Knuth sec 4.5.2, exercise 15
	   (let* ((q (math-idivmod u3 v3))
		  (t1 (math-sub u1 (math-mul v1 (car q)))))
	     (setq u1 v1  u3 v3  v1 t1  v3 (cdr q))))
	 (let ((q (math-idivmod a u3)))
	   (and (eq (cdr q) 0)
		(math-mod (math-mul (car q) u1) m))))))

(defun math-mod-intv (a b)
  (let* ((q1 (math-floor (math-div (nth 2 a) b)))
	 (q2 (math-floor (math-div (nth 3 a) b)))
	 (m1 (math-sub (nth 2 a) (math-mul q1 b)))
	 (m2 (math-sub (nth 3 a) (math-mul q2 b))))
    (cond ((equal q1 q2)
	   (math-sort-intv (nth 1 a) m1 m2))
	  ((and (math-equal-int (math-sub q2 q1) 1)
		(math-zerop m2)
		(memq (nth 1 a) '(0 2)))
	   (math-make-intv (nth 1 a) m1 b))
	  (t
	   (math-make-intv 2 0 b)))))

;; The variables math-exp-str and math-exp-pos are local to
;; math-read-exprs in math-aent.el, but are used by
;; math-read-angle-brackets, which is called (indirectly) by
;; math-read-exprs.
(defvar math-exp-str)
(defvar math-exp-pos)

(defun math-read-angle-brackets ()
  (let* ((last (or (math-check-for-commas t) (length math-exp-str)))
	 (str (substring math-exp-str math-exp-pos last))
	 (res
	  (if (string-match "\\` *\\([a-zA-Z#][a-zA-Z0-9#]* *,? *\\)*:" str)
	      (let ((str1 (substring str 0 (1- (match-end 0))))
		    (str2 (substring str (match-end 0)))
		    (calc-hashes-used 0))
		(setq str1 (math-read-expr (concat "[" str1 "]")))
		(if (eq (car-safe str1) 'error)
		    str1
		  (setq str2 (math-read-expr str2))
		  (if (eq (car-safe str2) 'error)
		      str2
		    (append '(calcFunc-lambda) (cdr str1) (list str2)))))
	    (if (string-match "#" str)
		(let ((calc-hashes-used 0))
		  (and (setq str (math-read-expr str))
		       (if (eq (car-safe str) 'error)
			   str
			 (append '(calcFunc-lambda)
				 (calc-invent-args calc-hashes-used)
				 (list str)))))
	      (math-parse-date str)))))
    (if (stringp res)
	(throw 'syntax res))
    (if (eq (car-safe res) 'error)
	(throw 'syntax (nth 2 res)))
    (setq math-exp-pos (1+ last))
    (math-read-token)
    res))

(provide 'calc-forms)

;;; calc-forms.el ends here